Annotation of rpl/lapack/lapack/zptsv.f, revision 1.11

1.9       bertrand    1: *> \brief \b ZPTSV
                      2: *
                      3: *  =========== DOCUMENTATION ===========
                      4: *
                      5: * Online html documentation available at 
                      6: *            http://www.netlib.org/lapack/explore-html/ 
                      7: *
                      8: *> \htmlonly
                      9: *> Download ZPTSV + dependencies 
                     10: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/zptsv.f"> 
                     11: *> [TGZ]</a> 
                     12: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/zptsv.f"> 
                     13: *> [ZIP]</a> 
                     14: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/zptsv.f"> 
                     15: *> [TXT]</a>
                     16: *> \endhtmlonly 
                     17: *
                     18: *  Definition:
                     19: *  ===========
                     20: *
                     21: *       SUBROUTINE ZPTSV( N, NRHS, D, E, B, LDB, INFO )
                     22: * 
                     23: *       .. Scalar Arguments ..
                     24: *       INTEGER            INFO, LDB, N, NRHS
                     25: *       ..
                     26: *       .. Array Arguments ..
                     27: *       DOUBLE PRECISION   D( * )
                     28: *       COMPLEX*16         B( LDB, * ), E( * )
                     29: *       ..
                     30: *  
                     31: *
                     32: *> \par Purpose:
                     33: *  =============
                     34: *>
                     35: *> \verbatim
                     36: *>
                     37: *> ZPTSV computes the solution to a complex system of linear equations
                     38: *> A*X = B, where A is an N-by-N Hermitian positive definite tridiagonal
                     39: *> matrix, and X and B are N-by-NRHS matrices.
                     40: *>
                     41: *> A is factored as A = L*D*L**H, and the factored form of A is then
                     42: *> used to solve the system of equations.
                     43: *> \endverbatim
                     44: *
                     45: *  Arguments:
                     46: *  ==========
                     47: *
                     48: *> \param[in] N
                     49: *> \verbatim
                     50: *>          N is INTEGER
                     51: *>          The order of the matrix A.  N >= 0.
                     52: *> \endverbatim
                     53: *>
                     54: *> \param[in] NRHS
                     55: *> \verbatim
                     56: *>          NRHS is INTEGER
                     57: *>          The number of right hand sides, i.e., the number of columns
                     58: *>          of the matrix B.  NRHS >= 0.
                     59: *> \endverbatim
                     60: *>
                     61: *> \param[in,out] D
                     62: *> \verbatim
                     63: *>          D is DOUBLE PRECISION array, dimension (N)
                     64: *>          On entry, the n diagonal elements of the tridiagonal matrix
                     65: *>          A.  On exit, the n diagonal elements of the diagonal matrix
                     66: *>          D from the factorization A = L*D*L**H.
                     67: *> \endverbatim
                     68: *>
                     69: *> \param[in,out] E
                     70: *> \verbatim
                     71: *>          E is COMPLEX*16 array, dimension (N-1)
                     72: *>          On entry, the (n-1) subdiagonal elements of the tridiagonal
                     73: *>          matrix A.  On exit, the (n-1) subdiagonal elements of the
                     74: *>          unit bidiagonal factor L from the L*D*L**H factorization of
                     75: *>          A.  E can also be regarded as the superdiagonal of the unit
                     76: *>          bidiagonal factor U from the U**H*D*U factorization of A.
                     77: *> \endverbatim
                     78: *>
                     79: *> \param[in,out] B
                     80: *> \verbatim
                     81: *>          B is COMPLEX*16 array, dimension (LDB,NRHS)
                     82: *>          On entry, the N-by-NRHS right hand side matrix B.
                     83: *>          On exit, if INFO = 0, the N-by-NRHS solution matrix X.
                     84: *> \endverbatim
                     85: *>
                     86: *> \param[in] LDB
                     87: *> \verbatim
                     88: *>          LDB is INTEGER
                     89: *>          The leading dimension of the array B.  LDB >= max(1,N).
                     90: *> \endverbatim
                     91: *>
                     92: *> \param[out] INFO
                     93: *> \verbatim
                     94: *>          INFO is INTEGER
                     95: *>          = 0:  successful exit
                     96: *>          < 0:  if INFO = -i, the i-th argument had an illegal value
                     97: *>          > 0:  if INFO = i, the leading minor of order i is not
                     98: *>                positive definite, and the solution has not been
                     99: *>                computed.  The factorization has not been completed
                    100: *>                unless i = N.
                    101: *> \endverbatim
                    102: *
                    103: *  Authors:
                    104: *  ========
                    105: *
                    106: *> \author Univ. of Tennessee 
                    107: *> \author Univ. of California Berkeley 
                    108: *> \author Univ. of Colorado Denver 
                    109: *> \author NAG Ltd. 
                    110: *
                    111: *> \date November 2011
                    112: *
                    113: *> \ingroup complex16OTHERcomputational
                    114: *
                    115: *  =====================================================================
1.1       bertrand  116:       SUBROUTINE ZPTSV( N, NRHS, D, E, B, LDB, INFO )
                    117: *
1.9       bertrand  118: *  -- LAPACK computational routine (version 3.4.0) --
1.1       bertrand  119: *  -- LAPACK is a software package provided by Univ. of Tennessee,    --
                    120: *  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
1.9       bertrand  121: *     November 2011
1.1       bertrand  122: *
                    123: *     .. Scalar Arguments ..
                    124:       INTEGER            INFO, LDB, N, NRHS
                    125: *     ..
                    126: *     .. Array Arguments ..
                    127:       DOUBLE PRECISION   D( * )
                    128:       COMPLEX*16         B( LDB, * ), E( * )
                    129: *     ..
                    130: *
                    131: *  =====================================================================
                    132: *
                    133: *     .. External Subroutines ..
                    134:       EXTERNAL           XERBLA, ZPTTRF, ZPTTRS
                    135: *     ..
                    136: *     .. Intrinsic Functions ..
                    137:       INTRINSIC          MAX
                    138: *     ..
                    139: *     .. Executable Statements ..
                    140: *
                    141: *     Test the input parameters.
                    142: *
                    143:       INFO = 0
                    144:       IF( N.LT.0 ) THEN
                    145:          INFO = -1
                    146:       ELSE IF( NRHS.LT.0 ) THEN
                    147:          INFO = -2
                    148:       ELSE IF( LDB.LT.MAX( 1, N ) ) THEN
                    149:          INFO = -6
                    150:       END IF
                    151:       IF( INFO.NE.0 ) THEN
                    152:          CALL XERBLA( 'ZPTSV ', -INFO )
                    153:          RETURN
                    154:       END IF
                    155: *
1.8       bertrand  156: *     Compute the L*D*L**H (or U**H*D*U) factorization of A.
1.1       bertrand  157: *
                    158:       CALL ZPTTRF( N, D, E, INFO )
                    159:       IF( INFO.EQ.0 ) THEN
                    160: *
                    161: *        Solve the system A*X = B, overwriting B with X.
                    162: *
                    163:          CALL ZPTTRS( 'Lower', N, NRHS, D, E, B, LDB, INFO )
                    164:       END IF
                    165:       RETURN
                    166: *
                    167: *     End of ZPTSV
                    168: *
                    169:       END

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